[M_a_t_t]

I don't what the purspose of the strakes are. In a different video (and on here somewhere) Mr. Edgar used them to help with turbulence on the outsides (I think attributed to the wheels) that caused seperation on his insights undertray.

Unless the air is able to be reattached to the rear section then I don't think having the diffuser would help much. The stock middle section (no stock covers? Maybe from a hybrid model?) might be too rough to allow the rear diffuser to help any. Hard to say. Its best to just try something.

I would probably start at the front and work my way back. Even if you just skip under the engine bay. Given enough space (or length of the rest of the car) the air might reattach underneath the car and allow the diffuser to work at full capacity.